'Fifties' in the Bible

and God turneth round the people the way of the wilderness of the Red Sea, and by fifties have the sons of Israel gone up from the land of Egypt.

And thou -- thou dost provide out of all the people men of ability, fearing God, men of truth, hating dishonest gain, and hast placed these over them, heads of thousands, heads of hundreds, heads of fifties, and heads of tens,

and Moses chooseth men of ability out of all Israel, and maketh them chiefs over the people, heads of thousands, heads of hundreds, heads of fifties, and heads of tens,